BASICS OF MRI - HOW MRI WORKS - MRI CONCEPTS
Based on gyromagnetic property of protons(or hydrogen nucleus, H+) It can be plain MRI or contrast MRI .M/c contrast agents used is i.v. Gadolinium Proton Density and relaxation time are assessed by radiofrequency pulse and the computer generates a grayscale image from this data. Magnetic field used in the range of .15 to 1.5 tesla Relaxation time: T1:Time taken to return to original axis(T1 images are used to find out normal anatomical details)It has got high soft tissue discrimination(CSF looks black) T2:Time taken by protons to displace. Used to asses pathological process.(fluid looks white) Characteristics of MR signals CSF: Hypo Intense on T1W1 and vice versa(T2 scan shows whiter) Fat:Hyper intense on T1W1(T1 scan shows whiter) C/I-patients with prosthesis in the body , metallic foreign bodies, pacemaker, cochlear implants, cranial aneurysm clips should never undergo MRI. Claustrophobia common with MRI. There are no beam hardening artefacts in MRI as in CT. MRI is a su...